微生物在粉土粉细砂中成膜阻渗机理及调控机制研究

微生物能附着于多孔介质表面形成生物膜占据孔隙体积，进而降低其渗透系数，但前期研究中载体大都为单一无机材料，微生物固着量较少，渗透性降幅有限，且生物膜形成机理及影响因素等尚不明确。因此本项目将引入有机纤维与传统粉土粉细砂组成复合材料，首先测试纤维种类、含量及土体改性条件下生物膜渗透特性及变化规律，建立土体改性材料表面理化特性、微生物固着分布规律及渗透系数之间相关关系，以期增大微生物固着量及生物膜形成厚度，大幅降低复合材料渗透系数；基于复合材料形成生物膜，进一步探究其渗透性对环境条件的响应，考虑影响因素包括土体种类、粒径分布、水头、酸碱性、溶质特性、营养寡等；同时对复合材料及生物膜结构进行细观表征，从宏微观两层面、物理化学生物多角度揭示微生物固着成膜机理，进而提出生物膜阻渗的调控机制。研究成果在黏土匮乏地区老旧垃圾堆场竖向防渗补强方面具有极高的现实价值，在城市生态文明建设方面应用前景广阔。

Microorganism has the potential to attach on the surface of porous medium, and reduces the pore size, finally causes the reduction of hydraulic conductivity. However, according to previous research, there was no significant effect of microbes on the hydraulic conductivity towards pure inorganic material, while the attached bacteria quantity is limited, and the mechanism of biofilm formation is also not clear. Thus, in this study, organic-fiber is introduced to promote the attached microbe quantity and biofilm thickness, in order to reduce the hydraulic conductivity of the fine sand substantially. Based on the fiber type, content and soil conditions, the hydraulic conductivity of biofilm are evaluated, and the relationship between the surface physicochemical properties of modified materials, distribution of microorganism and hydraulic behavior will be established. Different factors towards hydraulic conductivity of biofilm are taken into account, including soil type, particle size distribution, water head, solute properties and nutrition concentration. Together with the physical, chemical and biological properties as well as the test results, further discussion will be made about the mechanism of biofilm formation and its effect on hydraulic conductivity. The results have important practical value for the construction of cut-off wall, especially in the clay deficient area.